1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive porcelain composition, a piezoelectric/electrostrictive article and a piezoelectric/electrostrictive film type element, and more particularly, it relates to a piezoelectric/electrostrictive porcelain composition capable of manufacturing a piezoelectric/electrostrictive article or a piezoelectric/electrostrictive film type element which exhibits superior piezoelectric/electrostrictive characteristics and in which even environments are taken into consideration, and a piezoelectric/electrostrictive article and a piezoelectric/electrostrictive film type element using this composition.
2. Description of the Related Art
Heretofore, a piezoelectric/electrostrictive element has been known as an element which can control a micro displacement of an order of sub-microns. In particular, a piezoelectric/electrostrictive film type element is preferable for the control of the micro displacement, and it is to be noted that in the above element, a piezoelectric/electrostrictive portion constituted of a piezoelectric/electrostrictive porcelain composition, and an electrode portion to which a voltage is applied are layered on a substrate made of a ceramic. In addition, the above element has superior characteristics such as a high electromechanical conversion efficiency, a high-speed response, a high durability, and a reduced power consumption. These piezoelectric/electrostrictive elements are used in various applications such as a piezoelectric pressure sensor, a probe moving mechanism of a scanning tunnel microscope, a rectilinear guide mechanism in a super-precision working device, a servo valve for hydraulic control, a head of a VTR device, a pixel constituting a flat panel type image display device, and a head of an ink jet printer.
Moreover, various studies have been made as to the piezoelectric/electrostrictive porcelain composition constituting the piezoelectric/electrostrictive portion is variously investigated. For example, there is disclosed a Pb(Mg1/3Nb2/3)O3—PbZrO3—PbTiO3 ternary solid solution material (PZT-based composition), or a piezoelectric/electrostrictive porcelain composition in which a part of Pb in the composition is replaced with Sr, La or the like (see, e.g., Patent Documents 1, 2). As to the piezoelectric/electrostrictive portion itself as the most important portion which determines piezoelectric/electrostrictive characteristics of the piezoelectric/electrostrictive element, it is expected that the piezoelectric/electrostrictive element having superior piezoelectric/electrostrictive characteristics (e.g., piezoelectric d constant) can be obtained.
Additionally, the PZT-based composition unavoidably contains lead (Pb). Especially in recent years, there has been a tendency to regard as a problem an influence on global environments, such as elution of lead (Pb) by acid rain. Therefore, as a piezoelectric/electrostrictive material in which the influence on the environment is considered, there is disclosed a piezoelectric porcelain (or a piezoelectric porcelain composition) capable of providing a piezoelectric article or a piezoelectric element which exhibits satisfactory piezoelectric/electrostrictive characteristics without containing lead (Pb) (see, e.g., Patent Documents 3 to 6).
However, it is the state of the art that a large displacement, in the case of the piezoelectric article and the like obtained using the piezoelectric porcelain (or the piezoelectric porcelain composition) disclosed in Patent Documents 3 to 6, cannot be easily obtained, as compared with the piezoelectric article and the like obtained using the lead (Pb)-containing PZT-based composition. One cannot help saying that the PZT-based composition is superior in respect of superiority/inferiority of the piezoelectric/electrostrictive characteristics. Therefore, there has been a necessity of developing a piezoelectric/electrostrictive porcelain composition capable of obtaining a piezoelectric/electrostrictive article or a piezoelectric/electrostrictive element which exhibits superior piezoelectric/electrostrictive characteristics even in a case where lead (Pb) is not contained.
[Patent Document 1] JP-B-44-17103
[Patent Document 2] JP-B-45-8145
[Patent Document 3] JP-A-2003-221276
[Patent Document 4] JP-A-2003-277145
[Patent Document 5] JP-A-2002-68836
[Patent Document 6] JP-A-2004-244299